VEGF is unique among angiogenic growth factors because it disrupts endothelial barrier function. Therefore, we considered whether this property of VEGF might contribute to tumor cell extravasation and metastasis. To test this, mice lacking the Src family kinases Src or Yes, which maintain endothelial barrier function in the presence of VEGF, were injected intravenously with VEGF-expressing tumor cells. We found a dramatic reduction in tumor cell extravasation in lungs or livers of mice lacking Src or Yes. At the molecular level, VEGF compromises the endothelial barrier by disrupting a VE-cadherin–β-catenin complex in lung endothelium from wild-type, but not Yes-deficient, mice. Disrupting the endothelial barrier directly with anti–VE-cadherin both amplifies metastasis in normal mice and overcomes the genetic resistance in Yes-deficient mice. Pharmacological blockade of VEGF, VEGFR-2, or Src stabilizes endothelial barrier function and suppresses tumor cell extravasation in vivo. Therefore, disrupting Src signaling preserves host endothelial barrier function providing a novel host-targeted approach to control metastatic disease.

Recent studies have documented that grapes and grape juices are equally cardioprotective as red wine. The existing reports implicate that the skin and seeds of the grapes containing polyphenolic antioxidants are instrumental for the cardioprotective properties of grapes. The present study examines if the flesh of grapes also possesses any cardioprotective abilities. Three groups of randomly selected rats were fed, water only (control), flesh of the grapes (2.5 mg/kg b. wt.) or the skins (2.5 mg/kg b. wt.) for 30 days. At the end of the 30 days, isolated perfused hearts were made ischemic for 30 min followed by 2 h of reperfusion in the working mode. The results demonstrated that both flesh and skin of the grapes could protect the hearts from ischemic reperfusion injury as evidenced by improved postischemic ventricular recovery and reduced myocardial infarct size. High performance liquid chromatography (HPLC) revealed that skin and flesh contained comparative amounts of glucose, fructose, tartaric acid, malic acid, shikimic acid, and trans-caftaric acid. In addition, the flesh contained reduced amounts (compared to skin) of cis-coutaric, trans-coutaric, caffeic, p-coumaric, cinnamics, and catechin/epicatechin. Total polyphenolic index was also lower in flesh compared to skin. The anthocyanins were present exclusively in the skin. Electron paramagnetic resonance (EPR) spectrometry of hydroxy radicals indicated that both flesh and skins possessed equal amount of ROS scavenging activities. Total malonaldehyde content in the heart was reduced comparatively with either flesh or skin. The results indicate for the first time that the flesh of grapes are equally cardioprotective as skin, and antioxidant potential of skin and flesh of grapes are comparable with each other despite of the fact that flesh does not possess any anthocyanin activities.

In the developing myocardium, vascular endothelial growth factor (VEGF)-dependent neovascularization occurs by division of existing vessels, a process that persists for several weeks following birth. During this remodeling phase, mRNA expression of ␤3 integrin in the heart decreases significantly as vessel maturation progresses. However, in male mice lacking ␤3, coronary capillaries fail to mature and continue to exhibit irregular endothelial thickness, endothelial protrusions into the lumen, and expanded cytoplasmic vacuoles. Surprisingly, this phenotype was not seen in female ␤3-null mice. Enhanced VEGF signaling contributes to the ␤3-null phenotype, because these vessels can be normalized by inhibitors of VEGF or Flk-1. Moreover, intravenous injection of VEGF induces a similar IntroductionIntegrins often cooperate with angiogenic growth factor receptors and are critical components of signaling pathways leading to angiogenesis. 1 Integrins provide physical and chemical links between cells and extracellular matrix, serving as structural organizers, mechanotransducers, and signaling molecules. In this context, integrin-mediated signaling could uniquely affect the structure and function of an individual cell based on its microenvironment (extracellular matrix components, tissue oxygenation, and growth factor concentration) and expression of particular integrin subunits and/or growth factor receptors. Integrin ␣v␤3 is either absent or expressed at low levels on normal endothelial cells in vivo but is significantly elevated on the angiogenic blood vessels associated with wounds, inflammatory sites, 2 or tumors. 3 Accordingly, integrin ␣v␤3 antagonists promote tumor regression by inducing apoptosis of angiogenic blood vessels while sparing the quiescent endothelial cells on pre-existing vessels. 3,4 These results support the concept that ␣v␤3 regulates endothelial-cell survival to support tumor growth and angiogenesis.However, in apparent disagreement with studies using ␣v␤3 integrin antagonists, mice lacking ␤3 actually show an enhanced angiogenic response in tumors. 5 Despite this apparent controversy, ␤3-null mice provide an interesting tool to study the requirement of ␣v␤3 and ␣IIb␤3 in various tissues and cell types (reviewed by Hynes and Hodivala-Dilke 6 ). The ␤3-null mouse was originally described as a model of Glanzmann thrombasthenia, 7 a pathology that is often associated with impaired ␣IIb␤3 expression or function in platelets. The ␤3-null mouse shows defects in platelet aggregation and bleeding 7 as well as enhanced vascular endothelial growth factor (VEGF)-induced endothelial-cell migration, proliferation, permeability, and angiogenesis. 5,8 Enhanced tumor growth in ␤3-null mice has been attributed to increased endothelial-cell expression of the VEGF receptor Flk-1/KDR 9 and decreased macrophage infiltration. 9,10 ␤3-null mice also have enhanced inflammatory 11 and wound healing responses, 12 the latter due to increased fibroblast infiltration and increased TGF-␤1 expression. 12 Together, these result...

The signal cascade that triggers and mediates ischemic preconditioning (IPC) remains unclear. The present study investigated the role of the Src family of tyrosine kinases in IPC. Isolated and buffer-perfused rat hearts underwent IPC with three cycles of 5-min ischemia and 5-min reperfusion, followed by 30-min ischemia and 120-min reperfusion. The Src tyrosine kinase family-selective inhibitor PP1 was administered between 45 and 30 min before ischemia (early PP1 treatment) or for 15 min before IPC [early PP1-preconditioning (PC) treatment]. PP1 was also administered for 5 min before the sustained ischemia (late PP1 treatment) or after IPC (late PP1-PC treatment). Src kinase was activated after 30 min of ischemia in both the membrane and cytosolic fractions. Src kinase was also activated by IPC but was attenuated after the sustained ischemia. Early and late PP1 treatment inhibited Src activation after the sustained ischemia and reduced infarct size. Early PP1-PC inhibited Src activation after IPC but not after the sustained ischemia and blocked cardioprotection afforded by IPC. Late PP1-PC treatment abrogated IPC-induced activation of Src and protein kinase C (PKC)-epsilon in the membrane but not in the cytosolic fraction. This treatment modality abrogated Src activation after the sustained ischemia and failed to block cardioprotection afforded by IPC. These results suggest that Src kinase activation mediates ischemic injury but triggers IPC in the position either upstream of or parallel to membrane-associated PKC-epsilon.

Intramyocardial injection of B cells into early post-ischemic myocardium preserved cardiac function by cardiomyocyte salvage. Other BM MNC subtypes were either ineffective or suppressed cardioprotection conferred by an enriched B cell population.